The primary objective of this project is to establish the mechanism(s) controlling the kinetics of channel gating during the fast EPSC in sympathetic ganglion cells. These experiments will involve analysis of evoked fast EPSCs, agonist-induced current fluctuations, and voltage-jumps in the presence of constant agonist application. In brief, the proposed work will involve the following specifc experiments: 1. Experiments will be continued to compare the influence of membrane voltage and temperature on the kinetics of EPSC decay and acetylcholine-induced current fluctuations. This analysis is expected to provide estimates of the mean channel open time and single channel conductance for the nicotinic receptor-channel complex in sympathetic postganglionic neurons. 2. The voltage jump technique will be developed to analyze the kinetics of agonist action and also will be used to determine the mechanism of action of nicotinic antagonists such as hexamethonium and curare in the ganglion preparation. 3. Experiments will be initiated to evaluate the role of enzymatic removal transmitter by acetylcholinesterase as a factor influencing EPSC decay in the ganglion. In this series of experiments the temperature dependence and voltage dependence of EPSC decay will be compared prior to and following exposure to the cholinesterase inhibitor methane sulfonal fluoride. In separate experiments the influence of curarization on the prolongation of the EPSC by MSF exposure will be tested to determine whether buffered diffusion occurs in the ganglion preparation after cholinesterase inhibition.